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YouTube is full of gym fails; think exercisers falling off treadmills, misusing strength machines, and wearing wildly inappropriate clothing. But most workout mistakes are a little less...obvious—and they aren't made only by people who are totally clueless about working out. Your friend who runs 20 miles a week or the woman you always see at the weight rack can be just as prone to errors that lead to injury as a gym newbie. Here, physical therapists reveal the seven most common ways their patients—even the super-fit ones—hurt themselves while working out.

They don't bother to warm up

It's tempting to skimp on a warm-up when you're time-crunched and want to maximize your precious gym minutes. Bad move: “The worst thing you can do is start cranking out the weights without getting your muscles ready,” says Karen Joubert, a Beverly Hills, Calif.-based physical therapist. That’s especially true when you work out after a day at the office, when your muscles are tight from eight hours of sitting.

Get your body ready for action with a dynamic warm-up. David Reavy, a Chicago-based physical therapist, gave us one of his favorite moves: Get into a lunge position, then fold your body forward to touch your toes. This lengthens the hip flexor in your back leg and engages the posterior chain (a group of muscles in the back of your body). (Check out six more dynamic stretches to prep you for any workout.)

They work themselves too hard

You just hit a back squat PR—and immediately add two more plates to the barbell to try to max it out even more. “We think if we lift heavier weights and push ourselves harder, we’re going to see quicker results,” says Joubert. “But really we’re going to see quicker injuries.” Her advice: “Play smarter, not harder.”

But how do you know when the time is right to take it to the next level? Wait until workouts start to feel too easy, says Reavy, and then focus on moving up gradually. If you’re running 3 miles at an 8 minute pace, for example, either up your distance by a mile or two at the same speed, or run faster for the same distance. The same goes for weight training; either bump up reps or pounds. “You have to give your body time to adapt to a new challenge,” Reavy says.

They let their form break

Can't eke out one more deadlift without rounding your lower back, or one more squat without leaning forward? Best to either lighten your load, or even call it quits for the day—lifting with poor form opens you up to injury, says Reavy. When you're lifting weights, remember to keep your spine straight and weight in your heels, and if you're unsure whether you're keeping correct form, enlist the help of a trainer.

They push past the pain

Is it muscle soreness or something more serious? Here's a rule of thumb: Soreness may linger a day or two before going away, but pain persists, says Joubert. Soreness also tends to be relieved by stretching and movement, while an injury will actually get worse. And if you get a pain that is sharp and shooting, then you know you’re causing some damage, says Reavy. “Or any pain that travels, like something that starts in your leg and moves up.”

That said, muscle soreness could be a bad sign as well, especially if you notice it in one leg and not the other, says Reavy. This could be a sign you’re compensating on one side for an injury on the other.

While you may be tempted to really push yourself to reach results, the key is to check in with your body and take a breather if something feels off, says Joubert. The bottom line: working through the pain doesn’t make you stronger; it makes you injured.

They don’t take a recovery day

In the same way it’s important to take a break when your body is hurting, it’s also crucial to give yourself some regular R&R. While skipping a workout or taking a day off may seem counterproductive to your goals, “It’s actually just as important, because you won’t see changes if you don’t give yourself a break,” says Joubert. “If you push your body in that gym every day, what happens is it starts to tear down, because you’re not giving the muscle cells time to rebuild and grow.” She recommends focusing on adequate hydration, getting plenty of electrolytes along with clean foods, and resting.

That said, a recovery day doesn’t need to be a lazy day. Reavy actually likes to have what he calls “mobility days,” which involves a combination of activation exercises, muscle releases, and mobilization workouts. To activate his muscles, he revisits his go-to functional warm-up. Then, he releases tension in various parts of his body using a foam roller. Finally, he gets to the main event, mobility training, mainly focusing on his hips and pelvis. Here are two of his favorites that you can try out for yourself:

Ilium Mobilization Against Wall: Place the back of your hip against a wall so that the back hipbone is firmly pressed into the wall. Keeping your spine neutral, bend forward as far as you can only at the hip, while maintaining the firm pressure of the back hipbone into the wall. Return to the starting position. Repeat.

SI Mobilization Backbend: Place one foot behind you with the heel slightly raised. Reach back with the arm of the same side and place a fist on the center of your sacrum. Lean back as far as you can so that your spine is extended. This is the starting position. Rotate your upper body to the side you are mobilizing, and return to the starting position. Repeat on both sides.

They don’t cross-train

As obsessed with SoulCycle as you may be, doing one workout—and only one workout—will backfire eventually. “If you’re doing the same thing over and over again, even you’re using your body properly, you’re strengthening the same muscles over and over again which can lead to tightness,” says Reavy. You might also wind up with an overuse injury, like tendonitis or shin splints, Joubert says.

As an alternative, they both strongly suggest cross training. And when choosing your mix of exercises, just be sure you keep them balanced. “Your body needs to lengthen and shorten its muscles,” Reavy says. “So if you’re often lifting heavy weights (shortening), go take a yoga or Pilates class (lengthening) as a counterbalance.”

Cross training is really a win-win, says Joubert: You’ll see better results, and your body won’t get burned out by doing the same thing constantly.

They wear the wrong shoes

Different shoes are best for different kinds of workouts. Running shoes are designed with flexible fabrics and for straight-line motion, so wearing them to, say, a boxing class that requires side-to-side bounding sets you up for a rolled ankle. Invest in a set of cross-training shoes—your body will thank you.